title: Inhibition of cadmium ion uptake in rice (Oryza sativa) cells by a wall-bound form of silicon.
abstract: The stresses acting on plants that are alleviated by silicon (Si) range from biotic to abiotic stresses, such as heavy metal toxicity. However, the mechanism of stress alleviation by Si at the single-cell level is poorly understood. We cultivated suspended rice (Oryza sativa) cells and protoplasts and investigated them using a combination of plant nutritional and physical techniques including inductively coupled plasma mass spectrometry (ICP-MS), the scanning ion-selective electrode technique (SIET) and X-ray photoelectron spectroscopy (XPS). We found that most Si accumulated in the cell walls in a wall-bound organosilicon compound. Total cadmium (Cd) concentrations in protoplasts from Si-accumulating (+Si) cells were significantly reduced at moderate concentrations of Cd in the culture medium compared with those from Si-limiting (-Si) cells. In situ measurement of cellular fluxes of the cadmium ion (Cd(2+) ) in suspension cells and root cells of rice exposed to Cd(2+) and/or Si treatments showed that +Si cells significantly inhibited the net Cd(2+) influx, compared with that in -Si cells. Furthermore, a net negative charge (charge density) within the +Si cell walls could be neutralized by an increase in the Cd(2+) concentration in the measuring solution. A mechanism of co-deposition of Si and Cd in the cell walls via a [Si-wall matrix]Cd co-complexation may explain the inhibition of Cd ion uptake, and may offer a plausible explanation for the in vivo detoxification of Cd in rice.
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Liu
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Ma
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
authors.forename: Congwu
authors.initials: C
authors.lastname: He
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
authors.forename: Xiuli
authors.initials: X
authors.lastname: Li
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
authors.forename: Wenjun
authors.initials: W
authors.lastname: Zhang
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.|National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
authors.forename: Fangsen
authors.initials: F
authors.lastname: Xu
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Lin
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
authors.forename: Lijun
authors.initials: L
authors.lastname: Wang
mesh_terms: D000222:Adaptation, Physiological; D001692:Biological Transport; D002104:Cadmium / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism*; D007477:Ions / Q000378:metabolism*; D012275:Oryza / Q000378:metabolism* / Q000502:physiology; D059828:Plant Cells / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D012825:Silicon / Q000378:metabolism* / Q000502:physiology
chemical_list: D007477:Ions; D002104:Cadmium; D012825:Silicon
keywords: Si-wall-Cd complexation; cadmium (Cd); cell wall; organosilicon; rice (Oryza sativa); silicon (Si)